Before FOTR, I heard rumors that Arwen was to be made into Xena the Warrior Princess, and was alarmed. Now, I believe the substitution of Arwen for Glorfindel was an inspiration. PJ is pulling the legend of Luthien and Beren from other Tolkein writings and making Arwen more Luthien...If you recall, she was the initiator of lots of adventure. So it's not like PJ is making a more active Arwen from nothing.
One problem with LOTR was the poor dramatization of the relationship of Aragorn and Arwen...we are left to the appendices to figure it out and to discern her characterization. When I read LOTR for the first time as a teen, I thought, "And Aragorn rejected Eowyn for this figure?". Took the appendix to explain it.
There's no way an audience that isn't immersed in Tolkein (like me) could accept Aragorn's eventual rejection of Eowyn with no sense of who Arwen is and the sacrifices she is making (losing her immortality, her Elfhood, and her family to the West)...I think PJ has a workable answer here. Movies have to be different from books, to show instead of tell.
I've been reading of other changes that bother me more than drawing Arwen as a more active character...like elimination of the Scouring of the Shire, Killing Saruman on some sort of wheel in TTT...
I can't wait to see the ents!
You are right, before FoTR came out, everyone was making the worst out of the Arwen situation, and I think it was handled really well...
Have you read the official TTT spoiler thread?
http://www.freerepublic.com/focus/chat/686059/posts
We are keeping track of the rumors there and talking about them.
As for the Scouring, I agree, it doesn't make much sense yet at face value to skip it. We have talked about it on that thread above. I am giving PJ the benefit of the doubt on this one that he will treat the rest of the story as wonderfully as he did the first part... the movie will have a nice end.